1. Field of the Invention
This invention relates to a device for maintaining alignment between reciprocating mold halves.
2. Description of Prior Art
Alignment interlocks are used on reciprocating equipment, such as injection molds, to first make contact with opposing sides of the alignment interlock and then engage to lift misaligned mold halves into alignment.
Such alignment interlocks are not limited to injection molds, and may be beneficial in stamping dies, blow molds, die cast dies, etc. Reciprocating equipment and/or machine tools, such as molds for use with injection molding, blow molding, stamping and similar processes involving opposing mold halves generally include at least one and often two machine platens. Conventional molding machines often involve a moving platen and a stationary platen. All molding machine platens sag to varying degrees, with typically the most misalignment present with the movable platen, due to platen bushing wear. Alignment interlocks within the mold are applied to opposing or engaging mold halves or platens to engage and then lift the mold into proper registration. Conventional interlocks have inevitably worn and galled over time, resulting in interlock damage as well as damage to the mold's cavities and cores. Conventional interlock wear begins at the engagement point, and over time the galled surface increases from the point of initial contact to the remaining surface of the interlock.
The initial contact between conventional male and female interlocks has typically been comprised of a fillet radius on the male interlock, and a fillet radius on the female interlock. This fillet radius is always a “full radius”, and the typical range is between 1 mm-2 mm, and would not typically exceed this radius size, as that would take away from the remaining amount of straight wear surface present on the interlock. The two interlocks make initial contact at these two fillet radius points, such as shown in FIGS. 6A and 6B. In the case of 0.2 mm sag (or “M” for “misalignment”), there is a mold closing distance (or “LD” for “lifting distance”) of 0.8 mm for the interlock on the movable half to be forced up to the straight alignment surface of the stationary half interlock, located at the tangent points of the two radii, as shown in FIGS. 7A and 7B. It is during this travel of the Lifting Distance (“LD”) where wear begins.
At other times, a chamfer is present at the male and the female engagement points, with the size and angle typically being at 30 degrees or greater, based from typical chamfers in manufacturing, with a fillet radius typically of 0.3 mm. The angle at which the misaligned movable half interlock resides will vary, typically between 0.1 degrees and 0.3 degrees, and for this reason the two chamfered surfaces do not make flat contact. Instead, the two small fillet radii would be the initial contact, and for 0.08 mm Misalignment, a Lifting Distance would be 0.13 mm, as shown in FIGS. 8 and 9.
The shorter the Lifting Distance is for the Misalignment to be corrected, the higher the amount of destructive impact encountered from the initial contact point until the interlocks reach the position of the fillet radii tangent points. This collision creates the initial material particle disbursement that then will ball up and further generate additional particle disbursement, galling and wear.